Unknown error in Producer/Consumer program, believe it to be an infinite loop.
- by ray2k
Hello, I am writing a program that is solving the producer/consumer problem, specifically the bounded-buffer version(i believe they mean the same thing). The producer will be generating x number of random numbers, where x is a command line parameter to my program. At the current moment, I believe my program is entering an infinite loop, but I'm not sure why it is occurring. I believe I am executing the semaphores correctly.
You compile it like this:
gcc -o prodcon prodcon.cpp -lpthread -lrt
Then to run, ./prodcon 100(the number of randum nums to produce)
This is my code.
typedef int buffer_item;
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>
#define BUFF_SIZE 10
#define RAND_DIVISOR 100000000
#define TRUE 1
//two threads
void *Producer(void *param);
void *Consumer(void *param);
int insert_item(buffer_item item);
int remove_item(buffer_item *item);
int returnRandom();
//the global semaphores
sem_t empty, full, mutex;
//the buffer
buffer_item buf[BUFF_SIZE];
//buffer counter
int counter;
//number of random numbers to produce
int numRand;
int main(int argc, char** argv) {
/* thread ids and attributes */
pthread_t pid, cid;
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM);
numRand = atoi(argv[1]);
sem_init(&empty,0,BUFF_SIZE);
sem_init(&full,0,0);
sem_init(&mutex,0,0);
printf("main started\n");
pthread_create(&pid, &attr, Producer, NULL);
pthread_create(&cid, &attr, Consumer, NULL);
printf("main gets here");
pthread_join(pid, NULL);
pthread_join(cid, NULL);
printf("main done\n");
return 0;
}
//generates a randum number between 1 and 100
int returnRandom()
{
int num;
srand(time(NULL));
num = rand() % 100 + 1;
return num;
}
//begin producing items
void *Producer(void *param) {
buffer_item item;
int i;
for(i = 0; i < numRand; i++)
{
//sleep for a random period of time
int rNum = rand() / RAND_DIVISOR;
sleep(rNum);
//generate a random number
item = returnRandom();
//acquire the empty lock
sem_wait(&empty);
//acquire the mutex lock
sem_wait(&mutex);
if(insert_item(item))
{
fprintf(stderr, " Producer report error condition\n");
}
else
{
printf("producer produced %d\n", item);
}
/* release the mutex lock */
sem_post(&mutex);
/* signal full */
sem_post(&full);
}
return NULL;
}
/* Consumer Thread */
void *Consumer(void *param) {
buffer_item item;
int i;
for(i = 0; i < numRand; i++) {
/* sleep for a random period of time */
int rNum = rand() / RAND_DIVISOR;
sleep(rNum);
/* aquire the full lock */
sem_wait(&full);
/* aquire the mutex lock */
sem_wait(&mutex);
if(remove_item(&item)) {
fprintf(stderr, "Consumer report error condition\n");
}
else {
printf("consumer consumed %d\n", item);
}
/* release the mutex lock */
sem_post(&mutex);
/* signal empty */
sem_post(&empty);
}
return NULL;
}
/* Add an item to the buffer */
int insert_item(buffer_item item) {
/* When the buffer is not full add the item
and increment the counter*/
if(counter < BUFF_SIZE) {
buf[counter] = item;
counter++;
return 0;
}
else { /* Error the buffer is full */
return -1;
}
}
/* Remove an item from the buffer */
int remove_item(buffer_item *item) {
/* When the buffer is not empty remove the item
and decrement the counter */
if(counter > 0) {
*item = buf[(counter-1)];
counter--;
return 0;
}
else { /* Error buffer empty */
return -1;
}
}
